The current and frequency dependencies of the low frequency noise have been investigated in 4H-SiC p+-n junctions in the frequency range 100-104 Hz and at current densities from 10-4 to 101 A/cm2. Good quality of the p+-n diode under investigation has been ascertained by high value of the recombination time in the space charge region, &tgr;R ≈ 70 ns, extracted from current voltage characteristic. At small current densities j ⩽ 10-3 A/cm2, the spectral noise density SI ∝1/f3/2. At 10-3 A/cm2 < j < 10-2 A/cm2, the generation-recombination (GR) noise predominates. The amplitude of this GR noise non-monotonically depends on current. At j ⩾ 10-2 A/cm2, the 1/f (flicker noise) is dominant. A new model of GR noise of the recombination current in forward biased p-n junction has been proposed. The model assumes that a trap level located relatively close to the conduction band is responsible for the observed GR noise. The main contribution to the GR noise comes from the fluctuations of the charge state of the trap. The model describes well both current and frequency dependencies of the observed GR noise.
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